| abstract |
Paint binders having an intrinsic viscosity of from 8-15 ml/g which are water soluble upon neutralization with bases comprising the condensation reaction product of (A) 50-85% by weight of a polyester resin modified with 5-40% by weight of a polysiloxane of the general formula <IMAGE> wherein R is an alkyl, cycloalkyl, aryl or alkoxy radical, R1 is hydrogen or an alkyl radical and n is an integer of from 0-40; said modified polyester having a hydroxyl number of from about 50-400 mg KOH/g, an acid value of below about 10 mg KOH/g, and an intrinsic viscosity of from about 6-11 ml/g, measured in dimethylformamide at 20 DEG C.; and (B) 15-50% by weight of a film forming resin containing carboxyl groups to provide an acid value of from about 100-300 mg KOH/g and an intrinsic viscosity of from about 5-9 ml/g, measured in dimethylformamide at 20 DEG C.; the ratio of the intrinsic viscosity values of components (A) and (B) being governed by the relation eta A/ eta B=1.2 to 2.2. The paint binders, at a high solids content and with a high water to organic solvent ratio, have a viscosity sufficiently low to be suitable for spray applications. The paint binders in paint formulations provide paint films having good physical characteristics. |